On his last day as president, Barack Obama commuted the sentences of 330 federal inmates convicted of drug crimes, bringing his total to 1,715.

It means Obama has granted more commutations to more people than the last 12 presidents combined. More than 500 of them were serving life sentences.

"He wanted to do it. He wanted the opportunity to look at as many as he could to provide relief,'' said Neil Eggleston, Obama's White House counsel, in an interview in his West Wing office. "He saw the injustice of the sentences that were imposed in many situations, and he has a strong view that people deserve a second chance.''

For Obama, it was the last time he planned to exercise his presidential powers in any significant way. At noon on Friday at the Capitol, Obama will stand with President-elect Donald Trump as his successor is sworn in and Obama's chapter in history comes to an end.

To be eligible for a commutation under Obama's initiative, inmates had to have behaved well in prison and already served 10 years, although some exceptions to the 10-year rule were granted. They also had to be considered nonviolent offenders, although many were charged with firearms violations in relation to their drug crimes.

Obama personally reviewed the case of every inmate who received a commutation.

The early release is part of Obama's effort to correct what he views as unreasonably long mandatory minimum sentences.

His push to lessen the burden on nonviolent drug offenders reflects his long-stated view that the nation should remedy the consequences of decades of onerous sentencing rules that have put tens of thousands of Americans behind bars for far too long.